Transformer



- NOV. 17, 1931. l 'Q SCHMUTZ 1,832,662

TRANSFORMER Filed Feb. 15. 1950 n Oss/mr Schmutz.

'ATTORNEY l Patented-Nov. 17, 193i UNITED' STATES PATENT. orifice osxAR scHMUTz, orl BERLIN-SIEMENSSTADT, GERMANY, A,AssIefNoa To wnsTINGiroUsn ELECTRIC a MANUFACTURING ,czorllIrAN-Y,- A CORPORATION or PENNSYLVANIA V,TnANsromuuu Application led February 15, 1930, Serial No. 428,634, and in Germany March 19, 1 929.

.phases of an alternating-current circuit or in electrical apparatus connected ,to such circuits are well known.'

interrupting means to disconnect the faulty apparatus or portionof the circuit from the remaining portion of the circuit. It is preferable, in such cases, to use a single transformer rather than va plurality of trans-fA formers and lto so arrange all of the primary circuit conductors that they shall-be inductively related to asingle-corestructure surrounding them. So long as the currents in the primary conductors are balanced, the sum of the instantaneous currents will be zero, and no current willflow in the secondary winding of the transformer.

U nsymmetrical positioning of the primary conductors with respectto the core member, or an unsymmetrical load on the conductors, will create fluxes that are caused to traverse the secondary Winding of the current transformer. 'Current may thus be generated in the secondary winding of the transformer by the stray fluxes, that interlink only one of the primary conductors and, if suiiiciently large, will cause operation of the relays for removing a faulty portion of the circuit, even though -no fault has. occurred.

An object of my invention is to provide Y means for preventing stray fluxes from one or more vof a plurality of primary circuit conductors from energizing the core of a eurrent transfomer.

According to the invention, the creation of stray fluxes in the core member of the transformer by the primary circuit conductors is prevented by providing a shield or closed Such transformers .are frequently employed to actu'ate circuitmagnetic path, formedof laminated or other material of high magnetic permeability, and locating it between the conductors constituting the primary-winding circuit and the conductors 'constituting the secondary-winding circuit.l The conductors of these two circuits ar'e, therefore,- separated from one another by the shielding action of this inagnetic path, so that anystray fluxes created b v the primary circuit conductors will flow in the magnetic shield that is provided, and will not reach the core or the secondary winding ing a closed magnetic path and having an opening to receive the primary-winding conductors 2 and 3 vwhich represent the .two conductors of a single phase circuit. The

coils 4 and 5 constitutethe secondary winding of the transformer and may be connected to indicating instruments, or to control apparatus for effecting a desired operationiipon the occurrence of a fault in the primary circuit of the transformer. The unsymrnetrical positioning ofthe two conductors 2 and 3, with respect to the core member 1, causes unsymmetrical leakage fluxes 6 and 7 which traverse the core member and the secondary winding coil of the transformer, and generate currents therein which may be sutilcient to cause the operation of the signal or' control devices.

Fig. 2. of' the drawings shows a current transformer organized in accordance with my invention, in which a core 1l is energized from the primary-winding conductors 12 and 13, thus energizing the coils 14 and 15 of the secondary-winding circuit. A magnetic shield 16 is 'provided to forni a closed magnetic path of high permeability positioned between the conductors 12 and 13 which constitute the primary winding of the` ,current transformer, and the windings 14 and 15'which are Wound upon the core member 11 to constitute the secondary Winding of the transformer. Any stray luXes which may be caused by the-,unsymmetrical location of the primary conductors 12 and 13 Will pass through the magnetic shield 16, as indicated by the broken lines 17 and 18 and will be thereby prevented from passing through the winding of the secondary'circuit ot the transformer.

An unbalance in the current carried by the conductors 12' and 13 Will cause a iiux to travel through the magnetic circuit of the core 11 to producea current in the secondary Winding oi the transformer. This current Will be of the same magnitude as though the magnetic shield 16 were not present, as long as-magnetizing ampere turns of the primary Winding are the same. The shield will, therefore, provide protection against the penetration of stray fluxes into the secondary Winding but Will not prevent proper energization of the secondary Winding of the transformer upon the occurrence of a fault in the primary-Winding circuit. n v

Since modifications may b e made in the apparatus and circuits described Without departing from the spirit of my invention, I do not Wish to be limited otherwise than by the scope of the appended claims.

I claim as my invention:

1. In a current transformer, a core constituting a closed magnetic circuit, a plurality of primary-Winding conductors extending through said core, a conductor Wound about the core to form a secondary Winding, and a member constituting a closed magnetic circuit positioned between the primary- Winding conductors and the secondary-Winding conductors.

2. In a current transformer, a core of magnetic material, a plurality of circuit conductors for magnetizing said core, and a magnetic shield comprising a closed magnetic path about said conductors and positioned between said conductors and said core.

In a current transformer, a core constituting a closed magnetic circuit, alplurality of primary-circuit conductors forenergizing said core, and means for preventing luX other than the resultant flux from all of said conductors from entering said core.

several conductors of an alternating-current circuit, a secondary Winding formed aboutA 4. In a current transformer, a core constituting a closed magnetic circuit, a plurallty of primary-circuit conductors comprising the several conductors of an alternating-current' circuit, a secondary Winding inductively related to said core, and means for preventing leakage flux from said primary-circuit conductors from entering said core.

5. In a current transformer, a core constituting a closed magnetic circuit, a plurality of primary-circuit conductors extend- ,ing through said core and comprising the sol 

